Societies on different continents developed food production at different times. Diamond argues that these differences in the timing of food production were related to the advantages of guns, germs, and steel. First, the availability of more consumable calories led to more people because the society was able to feed more individuals. Similarly, the presence of domesticated animals allowed for a greater population because the livestock furnished meat, milk, fertilizer for other plants, and power by pulling plows that cultivated more plant food.

Indirectly, the sedentary life available through food production/agriculture allowed for shorter birth intervals and the storage of food surpluses. Stored food, in turn, allowed for the feeding of non-food-producing specialists, including soldiers, priests, bureaucrats, and kings.

Plant and animal domestication made direct contributions to wars of conquest. First, the domestication of horses allowed small groups of...